An agricultural harvester e.g., a plant cutting machine, including, but not limited to, a powered vehicle such as a combine or a windrower, generally includes a header operable for severing and collecting plant or crop material as the harvester is driven over a crop field. The header has a plant cutting mechanism, e.g., a cutter bar, for severing the plants or crops via, for example, an elongate sickle mechanism that reciprocates sidewardly relative to a non-reciprocating guard structure. After crops are cut, they are collected inside the header and transported via at least one conveyor such as a draper belt and/or an infeed belt towards a feederhouse located centrally inside the header.
Cutterbar knife drives oscillate first and second sickle mechanisms of cutterbars in opposite directions in order to cut crop. However, existing center knife drives often include a complicated gearbox with two shafts extending upward that oscillate back and forth and drive the two knives on the header. The two shafts protrude up from a relatively flat gearbox cover and have seals to keep oil in the gearbox and dirt out. These seals have proven to be difficult to keep working properly in certain conditions due to dirt accumulation. Once dirt gets past the seals and into the gearbox, bearings and other components become worn and result in failures that are costly and time-consuming to remedy. In addition, the complicated gearbox is relatively difficult to modify or to retrofit for different applications due to its design and manufacturing method.